The state-of-the-art Fe/N/C catalyst has presented comparable initial cathode performance to the benchmark Pt/C catalyst in proton exchange membrane fuel cells(PEMFCs).However,the major bottleneck is its significant a...The state-of-the-art Fe/N/C catalyst has presented comparable initial cathode performance to the benchmark Pt/C catalyst in proton exchange membrane fuel cells(PEMFCs).However,the major bottleneck is its significant activity decay in real-world PEMFC cells.The superposed“fast decay”and“slow decay”have been well documented to describe the degradation process of Fe/N/C catalysts during PEMFC operation.The fast decay has been well understood in close relation to the demetallation at the initial 15-h stability test.Nevertheless,it is still unclear how the remanent active sites evolve after demetallation.To this end,the catalyst performance and evolution of a typical Fe/N/C active site were herein investigated through postmortem characterizations of the membrane electrode assemblies(MEAs)after different operations.It is presented that 1 bar pressure and 80℃ temperature are the optimized conditions for Fe/N/C MEA.Particularly,the“fast decay”in the initial 15 h is immune to the various operating parameters,while the“slow decay”highly depends on the applied temperature and pressure.According to the X-ray absorption spectra(XAS)analysis and stability test of MEA,the gradual evolution of Fe-N coordination to Fe-O is found correlated with the“slow decay”and accounts for the catalyst decay after the demetallation process.展开更多
The drawbacks of conventional flow channel-rib flow fields and gas diffusion layers(GDLs)severely restrict mass transport and water management in proton exchange membrane fuel cells(PEMFCs),thereby limiting their volu...The drawbacks of conventional flow channel-rib flow fields and gas diffusion layers(GDLs)severely restrict mass transport and water management in proton exchange membrane fuel cells(PEMFCs),thereby limiting their volumetric power density.Our previous study proposed an ultrathin GDL-less PEMFC that uses metal foam to replace traditional flow fields and GDLs,significantly reducing mass transport distance and cell thickness while enhancing volumetric power density.To ensure contact and transition between the catalyst layer and metal foam,an ultrathin carbon nanofiber film(CNFF)is employed in this structure.This study systematically investigates the effect of CNFF thickness on the performance of ultrathin GDL-less PEMFCs.Results demonstrate that the protective effect of CNFF on the catalyst coated membrane(CCM)is strongly correlated with its thickness.Specifically,thinner CNFF offers less protection to the catalyst layer,resulting in an 30%difference in electrochemical active surface area(ECSA).A moderate increase in thickness reduces ohmic overpotential and enhances Knudsen diffusion within the oxygen catalyst layer,while excessive thickness leads to a decrease in oxygen molecular diffusion.Additionally,thicker CNFF provides better water storage and more effective water management under medium current densities,although performance degrades at ultrahigh current densities.Overall,the 25-μm CNFF balances these various factors to achieve the best integrated performance.These findings highlight that the optimal performance of GDL-less PEMFCs can be achieved by regulating the thickness of CNFF.展开更多
Design of catalyst layers(CLs)with high proton conductivity in membrane electrode assemblies(MEAs)is an important issue for proton exchange membrane fuel cells(PEMFCs).Herein,an ultrathin catalyst layer was constructe...Design of catalyst layers(CLs)with high proton conductivity in membrane electrode assemblies(MEAs)is an important issue for proton exchange membrane fuel cells(PEMFCs).Herein,an ultrathin catalyst layer was constructed based on Pt-decorated nanoporous gold(NPG-Pt)with sub-Debye-length thickness for proton transfer.In the absence of ionomer incorporation in the CLs,these integrated carbon-free electrodes can deliver maximum mass-specific power density of 198.21 and 25.91 kW·gPt^(-1) when serving individually as the anode and cathode,at a Pt loading of 5.6 and 22.0 pg·cm^(-2),respectively,comparable to the best reported nano-catalysts for PEMFCs.In-depth quantitative experimental measurements and finite-element analyses indicate that improved proton conduction plays a critical role in activation,ohmic and mass transfer polarizations.展开更多
Proton Exchange Membrane Fuel Cells(PEMFCs)are known as a promising alternative for internal combustion engines(ICE)to reduce pollution.Recent progress of PEMFCs is heading towards achieving higher power densities,red...Proton Exchange Membrane Fuel Cells(PEMFCs)are known as a promising alternative for internal combustion engines(ICE)to reduce pollution.Recent progress of PEMFCs is heading towards achieving higher power densities,reducing the refueling time,and decreasing the degradations,to facilitate the commercialization of hydrogen mobility.Model-assisted stack component development,diagnosis,and management are essential to ensure improved stack design and operation for tackling the existing implementation challenges of PEMFCs.Past reviews usually touched on a specific aspect,which can hardly provide the readers a complete picture of the key challenges and advances in water management.This paper aims at delivering a comprehensive source to review,from both experimental,analytical,and numerical viewpoints,the key operational challenges,and solutions of the stack to improve water/thermal management and cold start.In addition to presenting the fundamental theory to develop an analytical model,the recent advances in the flow field design,nanofluid coolants,and cold-start methods.Furthermore,the impacts of microstructural properties and the design of the porous layers on the water/thermal management are described.展开更多
The objective of this study is to investigate the potential reduction of polarization in proton exchange membrane fuel cells(PEMFCs)through the design optimization of flow channel.The impact of structural parameters a...The objective of this study is to investigate the potential reduction of polarization in proton exchange membrane fuel cells(PEMFCs)through the design optimization of flow channel.The impact of structural parameters and surface properties of the bipolar plate flow channels on the PEMFC performance is thoroughly examined on a commercial scale PEMFC with an active area of 203.49 cm2.The fabrication of bipolar plate flow channels with different structural and wetting properties is achieved using a novel ultrafast laser technique and a conventional milling method.Single cell stack is assembled and subjected to polarization curve tests.The findings indicate that decreasing the width of the flow channels generally improves the performance of commercial-scale PEMFCs.The minimum allowable channel width is dependent on the length of the flow channels.Interestingly,flow channels with higher hydrophilicity and surface adhesion do not necessarily lead to poorer water removal capability,which may be attributed to the formation of a thin water film on superhydrophilic channel surfaces.This research provides valuable insights into the design of optimal flow fields for commercial-scale PEMFCs.展开更多
Sustainable energy technologies,particularly fuel cells,are gaining attraction for their potential to reduce carbon emissions and provide efficient power.Proton exchange membrane fuel cells(PEMFCs)have been central to...Sustainable energy technologies,particularly fuel cells,are gaining attraction for their potential to reduce carbon emissions and provide efficient power.Proton exchange membrane fuel cells(PEMFCs)have been central to this development.However,one persistent issue with lowtemperature PEMFCs is the dehydration of Nafion ionomer at elevated temperatures,which severely limits proton conductivity.Wang et al.tackle this by introducing a covalent organic framework(COF)interwoven with Nafion,addressing the challenge of maintaining proton conductivity and oxygen transport in medium temperatures(100–120℃).展开更多
Anion exchange membrane fuel cells(AEMFCs),regarded as a promising alternative to proton exchange membrane fuel cells(PEMFCs),have garnered increasing attention because of their cost-effectiveness by using the non-nob...Anion exchange membrane fuel cells(AEMFCs),regarded as a promising alternative to proton exchange membrane fuel cells(PEMFCs),have garnered increasing attention because of their cost-effectiveness by using the non-noble metal catalysts and hydrocarbon-based ionomers as membrane[1].However,despite of extensive researches on non-noble metal catalysts such as Co[2].展开更多
基金financially supported by the Fundamental Re-search Funds for the Central Universities(No.2023CDJXY-016)the Outstanding Youth Project of Natural Science Foundation of Guangdong Province(Grant No.2022B1515020020).
文摘The state-of-the-art Fe/N/C catalyst has presented comparable initial cathode performance to the benchmark Pt/C catalyst in proton exchange membrane fuel cells(PEMFCs).However,the major bottleneck is its significant activity decay in real-world PEMFC cells.The superposed“fast decay”and“slow decay”have been well documented to describe the degradation process of Fe/N/C catalysts during PEMFC operation.The fast decay has been well understood in close relation to the demetallation at the initial 15-h stability test.Nevertheless,it is still unclear how the remanent active sites evolve after demetallation.To this end,the catalyst performance and evolution of a typical Fe/N/C active site were herein investigated through postmortem characterizations of the membrane electrode assemblies(MEAs)after different operations.It is presented that 1 bar pressure and 80℃ temperature are the optimized conditions for Fe/N/C MEA.Particularly,the“fast decay”in the initial 15 h is immune to the various operating parameters,while the“slow decay”highly depends on the applied temperature and pressure.According to the X-ray absorption spectra(XAS)analysis and stability test of MEA,the gradual evolution of Fe-N coordination to Fe-O is found correlated with the“slow decay”and accounts for the catalyst decay after the demetallation process.
基金support from the National Natural Science Foundation of China for Distinguished Young Scholars(52225604)the Jilin Province Science and Technology Development Program(grant No.20230301017ZD)the Marine Defense Innovation Fund of China Ship Development and Design Center(Grant No.2023712-01).
文摘The drawbacks of conventional flow channel-rib flow fields and gas diffusion layers(GDLs)severely restrict mass transport and water management in proton exchange membrane fuel cells(PEMFCs),thereby limiting their volumetric power density.Our previous study proposed an ultrathin GDL-less PEMFC that uses metal foam to replace traditional flow fields and GDLs,significantly reducing mass transport distance and cell thickness while enhancing volumetric power density.To ensure contact and transition between the catalyst layer and metal foam,an ultrathin carbon nanofiber film(CNFF)is employed in this structure.This study systematically investigates the effect of CNFF thickness on the performance of ultrathin GDL-less PEMFCs.Results demonstrate that the protective effect of CNFF on the catalyst coated membrane(CCM)is strongly correlated with its thickness.Specifically,thinner CNFF offers less protection to the catalyst layer,resulting in an 30%difference in electrochemical active surface area(ECSA).A moderate increase in thickness reduces ohmic overpotential and enhances Knudsen diffusion within the oxygen catalyst layer,while excessive thickness leads to a decrease in oxygen molecular diffusion.Additionally,thicker CNFF provides better water storage and more effective water management under medium current densities,although performance degrades at ultrahigh current densities.Overall,the 25-μm CNFF balances these various factors to achieve the best integrated performance.These findings highlight that the optimal performance of GDL-less PEMFCs can be achieved by regulating the thickness of CNFF.
基金financially supported by the National Natural Science Foundation of China(52073214,21603161,51671145,51761165012 and U1804255)the National Science Fund for Distinguished Young Scholars(No.51825102)the Tianjin Municipal Major Project of New Materials(No.16ZXCLGX00120).
文摘Design of catalyst layers(CLs)with high proton conductivity in membrane electrode assemblies(MEAs)is an important issue for proton exchange membrane fuel cells(PEMFCs).Herein,an ultrathin catalyst layer was constructed based on Pt-decorated nanoporous gold(NPG-Pt)with sub-Debye-length thickness for proton transfer.In the absence of ionomer incorporation in the CLs,these integrated carbon-free electrodes can deliver maximum mass-specific power density of 198.21 and 25.91 kW·gPt^(-1) when serving individually as the anode and cathode,at a Pt loading of 5.6 and 22.0 pg·cm^(-2),respectively,comparable to the best reported nano-catalysts for PEMFCs.In-depth quantitative experimental measurements and finite-element analyses indicate that improved proton conduction plays a critical role in activation,ohmic and mass transfer polarizations.
基金the European Union’s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No.754354.
文摘Proton Exchange Membrane Fuel Cells(PEMFCs)are known as a promising alternative for internal combustion engines(ICE)to reduce pollution.Recent progress of PEMFCs is heading towards achieving higher power densities,reducing the refueling time,and decreasing the degradations,to facilitate the commercialization of hydrogen mobility.Model-assisted stack component development,diagnosis,and management are essential to ensure improved stack design and operation for tackling the existing implementation challenges of PEMFCs.Past reviews usually touched on a specific aspect,which can hardly provide the readers a complete picture of the key challenges and advances in water management.This paper aims at delivering a comprehensive source to review,from both experimental,analytical,and numerical viewpoints,the key operational challenges,and solutions of the stack to improve water/thermal management and cold start.In addition to presenting the fundamental theory to develop an analytical model,the recent advances in the flow field design,nanofluid coolants,and cold-start methods.Furthermore,the impacts of microstructural properties and the design of the porous layers on the water/thermal management are described.
基金National Natural Science Foundation of China(No.52022050 and 52002210)Young Elite Scientists Sponsorship Program by CAST(No.2021QNRC001)2021 Independent research project of SVM.
文摘The objective of this study is to investigate the potential reduction of polarization in proton exchange membrane fuel cells(PEMFCs)through the design optimization of flow channel.The impact of structural parameters and surface properties of the bipolar plate flow channels on the PEMFC performance is thoroughly examined on a commercial scale PEMFC with an active area of 203.49 cm2.The fabrication of bipolar plate flow channels with different structural and wetting properties is achieved using a novel ultrafast laser technique and a conventional milling method.Single cell stack is assembled and subjected to polarization curve tests.The findings indicate that decreasing the width of the flow channels generally improves the performance of commercial-scale PEMFCs.The minimum allowable channel width is dependent on the length of the flow channels.Interestingly,flow channels with higher hydrophilicity and surface adhesion do not necessarily lead to poorer water removal capability,which may be attributed to the formation of a thin water film on superhydrophilic channel surfaces.This research provides valuable insights into the design of optimal flow fields for commercial-scale PEMFCs.
基金financial support from the National Natural Science Foundation of China(No.22301139)the Natural Science Foundation of Jiangsu Province(No.BK 20230375).
文摘Sustainable energy technologies,particularly fuel cells,are gaining attraction for their potential to reduce carbon emissions and provide efficient power.Proton exchange membrane fuel cells(PEMFCs)have been central to this development.However,one persistent issue with lowtemperature PEMFCs is the dehydration of Nafion ionomer at elevated temperatures,which severely limits proton conductivity.Wang et al.tackle this by introducing a covalent organic framework(COF)interwoven with Nafion,addressing the challenge of maintaining proton conductivity and oxygen transport in medium temperatures(100–120℃).
基金supported by the National Natural Science Foundation of China(Nos.22162014 and U24A2044).
文摘Anion exchange membrane fuel cells(AEMFCs),regarded as a promising alternative to proton exchange membrane fuel cells(PEMFCs),have garnered increasing attention because of their cost-effectiveness by using the non-noble metal catalysts and hydrocarbon-based ionomers as membrane[1].However,despite of extensive researches on non-noble metal catalysts such as Co[2].
文摘为了同时优化质子交换膜燃料电池(proton exchange membrane fuel cells,PEMFC)系统的效率和输出功率,文章首先建立PEMFC系统的机理模型,并分析系统效率和输出功率特性;其次针对传统灰狼算法(grey wolf optimizer,GWO)的初始化种群不均匀和易出现早熟收敛的问题,引入佳点集种群初始化策略和非线性收敛因子策略,并由此提出一种改进多目标灰狼优化算法(multi-objective grey wolf optimizer,MOGWO),有效改善了灰狼算法的搜索精度和收敛性能;然后针对改进多目标灰狼优化算法求得的Pareto最优解集,使用TOPSIS评价法得出逼近理想解的最佳解,确定PEMFC系统的最佳运行条件;最后对所提出的MOGWO算法进行仿真验证,结果表明该算法能够有效提高PEMFC系统在实际运行中的输出功率和系统效率。
